The contamination of the water resources in the United States with hazardous organic compounds continues to pose serious and widespread risks to public health and safety. Hazardous organic compounds include chlorinated solvents, hydrocarbons, disinfection byproducts, pesticides, polyaromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and other xenobiotic (not naturally occurring) organic chemicals. As these compounds comprise a majority of the 275 ?high-priority? hazardous substances ranked by the Agency of Toxic Substances and Disease Registry (ATSDR), the United States Environmental Protection Agency (US EPA) and state regulatory agencies have set ambitious treatment goals for these dangerous and often carcinogenic substances. In addition to increased risks for cancer, very small concentrations of hazardous organic compounds have been proven to cause various illnesses including liver or kidney disease, immune dysfunction, nervous system disorders, and hormonal or reproductive defects. The remediation of hazardous organic compounds is difficult and costly. Superfund site managers, municipalities and water suppliers across the country are demanding less expensive and more effective treatment options for hazardous organic compounds than the existing suite of energy-intense and waste-producing conventional technologies. Specifically, there is a need for new technologies to consolidate the treatment of multiple hazardous organic compounds into simple, environmentally friendly, and easy-to-use systems with as minimal process units as possible. This proposal seeks to address this need through a novel enhanced cometabolism technology. In contrast to conventional physical or chemical technologies such as air stripping and activated carbon, this new technology degrades the hazardous organic compounds into harmless byproducts instead of producing a concentrated secondary waste stream. Moreover, this new technology offers significant reductions in energy and maintenance costs compared with chemical or UV oxidation. Flexibly designed as both an in-situ and ex-situ treatment option, this new technology offers reliable performance across a range of dynamic operating conditions to achieve simultaneous degradation of hundreds of hazardous organic compounds. In this Phase II project, a scaled-up pilot plant is designed, constructed, optimized, and tested to treat hazardous organic compounds at a high-profile contaminated site. This project establishes the long-term performance profile for the new technology while engaging the pilot plant in a series of gold-standard stress tests to obtain key operational boundaries. Ultimately, the project establishes the detailed design criteria and technoeconomic analysis necessary for implementing this new technology to address a variety of urgent needs across the Superfund site, municipal drinking water, decentralized treatment, wastewater reuse and recycle, and agricultural and industrial water treatment sectors. The outcome of this project is the development of a first-of-its-kind technology for degrading complex combinations of hazardous organic compounds in water. The successful result of this project holds significant promise in addressing harmful contaminants that are not effectively treatable using existing technologies, and thereby securing substantial value for public and private environmental stewardship for future generations.